Filtering and forwarding frames at an optical network node

ABSTRACT

An optical line terminal (OLT) monitors and controls communications with a plurality of optical nodes (ONs), such as optical network units (ONUs) and/or optical network terminators (ONTs), within a passive optical network (PON), such as, but not exclusively, an Ethernet-based passive optical node (EPON). A tagging mechanism is implemented to identify an origin ON that introduces a frame into the PON segment linking the origin ON with the OLT. The origin ON produces a PON tag to associate its identifier (ON_ID) to the frame. The PON tag facilitates filtering and forwarding operations, and enables the physical layer interface (PHY) to the PON segment to emulate a point-to-point and/or shared communications link. The PON tag allows a MAC control layer to create virtual ports to traffic incoming and outgoing optical signals, and supply the virtual ports to a forwarding entity for frame filtering and forwarding. The PON tag also allows an OLT and ON to track the origination and/or destination of a frame within the PON segment, and accept or reject the frame based on the contents of the PON tag.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/339,442, filed Dec. 14, 2001, by Sala et al.,entitled “EPON Compliance Framework and Solution,” incorporated hereinby reference; U.S. Provisional Application No. 60/367,317, filed Mar.26, 2002, by Sala et al., entitled “EPON Compliance Framework andSolution,” incorporated herein by reference; and U.S. ProvisionalApplication No. 60/393,096, filed Jul. 3, 2002, by Gummalla et al.,entitled “System and Method for Supporting Security and Other Servicesin an Ethernet Passive Optical Network,” incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to communicationsnetworking, and more specifically, to filtering and forwarding frames inan optical network.

[0004] 2. Related Art

[0005] In regards to communications networks, there is a continuouschallenge to achieve an optimal balance among various networkcharacteristics. Such characteristics include bandwidth demand andquality of service parameters, such as latency, loss, or priority. Forexample, data-overcable networks presently are expanding the variety ofservices traditionally provided to subscribers. In addition totelevision broadcasts, cable providers are offering telephony,messaging, and Internet services. As a result, additional bandwidth isneeded to support the timely delivery of these services. Moreover,traditional cable broadcasts primarily require one-way communicationfrom a cable service provider to a subscriber's home. As interactive orpersonal television services and other nontraditional cable servicescontinue to be offered, communications media used to support one-waycommunications must now contend with an increased demand forbi-directional communications.

[0006] Optical networks are evolving as a solution to bandwidthlimitations prevalent on communication networks. For example, a passiveoptical network (PON) can be built to gain bandwidth efficiency andreduce protocol overhead. A typical PON consists of an optical lineterminal (OLT) that manages communications with a plurality of opticalnetwork units (ONUs). Conventional PON topology has a shared upstreamand a broadcast downstream. The ONUs have the opportunity to listen tothe downstream broadcasts. However, the OLT uses time divisionmultiplexing to enable the ONUs to send frames containing data and/orrequests in assigned slots in the upstream. Frames sent in the upstreamfrom one ONU are not seen by the other ONUs.

[0007] The communications path between an OLT and its ONUs is referredto as a PON segment. A conventional PON segment is neither apoint-to-point (P2P) segment nor a shared segment. In a typical sharedsegment, a frame is seen by all attached devices. In a PON segment,however, frames on the upstream are not seen by any other device. Whenupstream frames arrive at the OLT from a PON segment, the frames areprocessed, filtered and forwarded to the next destination. The OLT usesa forwarding entity (such as, a bridge or router) to execute thefiltering and forwarding operations. Conventional forwarding entitiesonly support P2P or shared segments, and as discussed, conventional PONsegments are neither. Therefore, conventional forwarding entities assumeall devices linked to one of its ports have seen any frame delivered tothat port. As a result, the forwarding entity will not send a frame backto the port that delivered the frame, even if a destination is an enduser linked to the incoming PON segment.

[0008] Therefore, a method and system are needed to address the aboveproblems.

SUMMARY OF THE INVENTION

[0009] The present invention solves the above problems by providing amethod, system, and computer program product for filtering andforwarding frames within an optical network. In the preferredembodiment, the optical network is a passive optical network (PON) suchas, but not exclusively, an Ethernet-based passive optical node (EPON).A tagging mechanism is implemented to uniquely identify an originoptical node that introduces a frame into the PON segment linking theorigin optical node with an upstream optical line terminal (OLT). Theorigin optical node produces a PON tag comprising its optical nodeidentifier (ON_ID). In an embodiment, the PON tag is included in theheader of the frame to produce a PON-tagged frame.

[0010] In an embodiment, the PON tag includes a PON tag type field and aPON tag control information field. The PON tag type field indicates thepresence of a PON tag. The PON tag control information field contains anON_ID, which is typically an ON_ID for the origin optical node. When aframe is first introduced into a PON segment, the origin optical nodetags the frame with a PON tag carrying its own ON_ID.

[0011] In an embodiment, the PON tag control information field alsoincludes fields for designating a mode and filtering operation. The modefield specifies whether the frame is to be, or has been, transportedover a point-to-point (P2P) communications path to a single destination,or a shared communications path to multiple destinations. The filteringoperation field specifies whether the frame is to be filtered by asource identifier or destination identifier. If the filtering operationfield is set to source identifier, the frame is filtered by the originON_ID, and if the filtering operation field is set to destinationidentifier, the frame is filtered by the ON_ID of a designatedrecipient.

[0012] The tagging mechanism of the present invention enables an OLTand/or an optical node (e.g., optical network unit or optical networkterminator) to recognize the origination and/or destination of aparticular frame. At a recipient optical node, acceptance or rejectionof a received frame is based on its PON tag. For example, if thefiltering operation field is set to source, an incoming frame isaccepted at a recipient optical node if the ON_ID specified in the PONtag control information field does not match the ON_ID of the recipientoptical node. If, on the other hand, the filtering operation field isset to destination, an incoming frame is accepted at a recipient opticalnode if the ON_ID specified in the PON tag control information fieldmatches the ON_ID of the recipient optical node.

[0013] In another embodiment, the PON control information field onlycontains two fields. A first field for specifying an ON_ID, and a secondfield for specifying a mode. If the mode field is set for P2P service, arecipient optical node accepts an incoming frame if the ON_ID fieldmatches the ON_ID assigned to the recipient optical node. Otherwise, theincoming frame is rejected. If, on the other hand, the mode field is setfor shared service, a recipient optical node accepts an incoming frameif the ON_ID field does not match the ON_ID assigned to the recipientnode. Otherwise, the incoming frame is rejected.

[0014] At an OLT, the mode (i.e., P2P or shared services) influences thefiltering and forwarding processes for all received frames. For P2Pservices, the destination for each internal and external frame isdetermined. The ON_ID field is modified to designate the destinationoptical node. The mode field is also checked to ensure that it is set toP2P mode. Afterwards, each frame is forwarded one-by-one to itsdestination optical node.

[0015] For shared services, all internal frames are sent downstream toall optical nodes operating on the shared path. The mode field ischecked to ensure that it is set to shared mode. Therefore, the presentinvention enables all PON-tagged traffic to be reflected back if it isreceived on a shared communications path. As for an externally-generatedframe, the OLT constructs a PON tag having a null ON_ID value or anuniversal identifier. The mode field is set to shared mode, and theexternal frame is broadcast to all optical nodes operating on the sharedpath.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0016] The accompanying drawings, which are incorporated herein and formpart of the specification, illustrate the present invention and,together with the description, further serve to explain the principlesof the invention and to enable a person skilled in the pertinent art tomake and use the invention. In the drawings, like reference numbersindicate identical or functionally similar elements. Additionally, theleftmost digit(s) of a reference number identifies the drawing in whichthe reference number first appears.

[0017]FIG. 1 illustrates an Ethernet-based optical network (EPON)according to an embodiment of the present invention.

[0018]FIG. 2a illustrates an Ethernet frame for transport over an EPONaccording to an embodiment of the present invention.

[0019]FIG. 2b illustrates a VLAN-tagged frame for transport over an EPONaccording to an embodiment of the present invention.

[0020]FIG. 2c illustrates a PON-tagged frame for transport over an EPONaccording to an embodiment of the present invention.

[0021]FIG. 2d illustrates a double tagged frame for transport over anEPON according to an embodiment of the present invention.

[0022]FIG. 2e illustrates a double tagged frame for transport over anEPON according to another embodiment of the present invention.

[0023]FIG. 2f illustrates a combined tagged frame for transport over anEPON according to an embodiment of the present invention.

[0024]FIG. 2g illustrates a combined tagged frame for transport over anEPON according to an embodiment of the present invention.

[0025]FIG. 3a illustrates a PON tag control information field of a frameaccording to an embodiment of the present invention.

[0026]FIG. 3b illustrates a PON tag control information field of a frameaccording to another embodiment of the present invention.

[0027]FIG. 4 illustrates an operational flow for producing and/orupdating a PON tag at an optical node according to an embodiment of thepresent invention.

[0028]FIG. 5 illustrates an operational flow for processing and/orupdating a PON tag upon reception at an OLT according to an embodimentof the present invention.

[0029]FIG. 6 illustrates an operational flow diagram for processingand/or updating a PON tag for transmission from an OLT according to anembodiment of the present invention.

[0030]FIG. 7 illustrates an operational flow diagram for processingand/or updating a PON tag upon reception at an optical node according toanother embodiment of the present invention.

[0031]FIG. 8 illustrates an optical node according to an embodiment ofthe present invention.

[0032]FIG. 9 illustrates an OLT according to an embodiment of thepresent invention.

[0033]FIG. 10 illustrates an example computer system useful forimplementing the present invention.

DETAILED DESCRIPTION OF THE INVENTION Table of Contents

[0034] I. Introduction

[0035] II. System Overview

[0036] III. Overview of PON Tagging

[0037] IV. Operational Flow for Optical Node PON Tag Construction

[0038] V. Processing Upstream PON Tag by OLT

[0039] VI. Processing Downstream PON Tag by an Optical Node

[0040] VII. System Architecture for ONU and OLT

[0041] VIII. Exemplary System Implementation

[0042] I. Introduction

[0043] The present invention implements a tagging mechanism that enablesthe physical layer interface (PHY) to a passive optical network (PON) toemulate a point-to-point and/or shared communications link. The taggingmechanism specifies an optical node identifier and a transmission mode,which collectively influence filtering and forwarding processes for eachframe bearing the tagging mechanism. If, for example, the transmissionmode is set to shared services, a forwarding entity (e.g., bridge,router, etc.) broadcasts the frame to all optical nodes operating on ashared path, regardless of who transmitted the frame.

[0044] Accordingly, the tagging mechanism permits a PON-aware forwardingentity to interact with a PON segment as if the segment is a sharedsegment and/or a point-to-point (P2P) segment even though a PON segmentis neither. Unlike a conventional forwarding entity, the PON-awareforwarding entity of the present invention does not assume all peershave seen an upstream frame. A conventional forwarding entity will nothand a frame to a destination port if it is the incoming port thatreceived the frame. However, in the present invention, a PON-awareforwarding entity reflects back all PON-tagged frames received from ashared path.

[0045] The tagging mechanism also enables a forwarding entity to receiveand process data and control messages as if they are coming from andgoing to multiple ports at the PON PHY interface when in reality thereis only one physical port. As such, the tagging mechanism allows a MACcontrol layer to create virtual ports (also called “logical ports”) totraffic incoming and outcoming optical signals, and supply the virtualports to the forwarding entity for filtering and/or forwarding. In anembodiment, the PON PHY interface includes multiple physical ports.However, the present invention allows the MAC control layer to createadditional virtual ports for one or more of the multiple physical ports,as required.

[0046] II. System Overview

[0047]FIG. 1 illustrates an Ethernet-based passive optical network(EPON) 100 according to an embodiment of the present invention. Althoughthe present invention is described with reference to an Ethernet-basedPON, the present invention can also be implemented in other opticalnetworks, including ATM-PON, active optical networks, etc.

[0048] EPON 100 includes an optical line terminal (OLT) 102 and one ormore widely distributed optical nodes (ON) 106 a-106 n (collectivelyreferred to as “optical node (ON) 106”). EPON 100 can be implemented inany media and/or multimedia distribution network. Furthermore, it shouldbe understood that the present invention can be implemented in anynetwork permitting the exchange of voice, data, video, audio, messaging,graphics, other forms of media and/or multimedia, or any combinationthereof.

[0049] OLT 102 is centrally positioned to command and controlinteractions with and among multiple ON 106. OLT 102 manages upstreamand/or downstream modulation and bandwidth allocation, and executesrules and policies for classifying and/or prioritizing communicationswith ON 106.

[0050] ON 106 includes an optical network unit (ONU), an optical networkterminator (ONT), or a combination of both. Each ON 106 is configurableto host one or more services to a subscriber end user. The servicesinclude telephony, television broadcasts, pay-for-view, video on demand,Internet communications (e.g., World Wide Web (WWW)), radio broadcasts,facsimile, file data transfer, electronic mailing services (email),messaging, video conferencing, live or time-delayed media feeds (suchas, speeches, debates, presentations, infomercials, news reports,sporting events, concerts, etc.), or the like. The subscriber end userincludes a home, business, multi-dwelling unit, building, or the like.

[0051] All communications transmitted in the direction from OLT 102towards ON 106 are referred to as being in the downstream. In anembodiment, the downstream is divided into one or more downstreamchannels. Each downstream channel is configured to carry various typesof information to ON 106. Such downstream information includestelevision signals, data packets (including IP datagrams), voicepackets, control messages, and/or the like. In an embodiment, thedownstream is formatted with an Ethernet entity. However, the presentinvention can be configured to support other data formats as would beapparent to one skilled in the relevant art(s).

[0052] In an embodiment, OLT 102 implements time division multiplexing(TDM) to transmit continuous point-to-multipoint signals in thedownstream. In another embodiment, OLT 102 implements wave divisionmultiplexing (WDM) or dense wave division multiplexing (DWDM) to supportcommunications with ON 106. In an embodiment, OLT 102 broadcasts signalsto all ON 106 or multicasts signals to two or more designated ON 106. Inanother embodiment, OLT 102 provides unicasts to a designated ON 106.

[0053] The upstream represents all communications from ON 106 towardsOLT 102. Each upstream channel carries bursts containing frames ofpackets from ON 106 to OLT 102. In the upstream, each frequency channelis broken into multiple assignable slots, and each ON 106 send a timedivision multiple access (TDMA) burst signal in an assigned slot. Eachassigned slot is synchronized so that upstream packets from each ON 106do not interfere with each other. Hence, ON 106 transmits by usinggrants issued by OLT 102. In another embodiment, WDM or DWDM isimplemented to support communications with OLT 102.

[0054] The communication path (representing the upstream and downstream)between OLT 102 and ON 106 is referred to as the “PON segment.” In anembodiment, ON 106 and OLT 102 assemble and transmit a burst of frame(s)within the PON segment over a fiber-optic link. A passive opticalsplitter/combiner 104 is provided to demultiplex or multiplexbi-directional communications with each individual ON 106. In anotherembodiment, free-space optics (FSO) technology provides the transmissionmedium that carries optical signals between OLT 102 and ON 106.

[0055] OLT 102 also routes signals from ON 106 to a destined locationover backbone network 110. Backbone network 110, as well as the pathbetween ON 106 and the subscriber end-users, is part of a wired,wireless, or combination of wired and wireless local area networks (LAN)or wide area networks (WAN), such as an organization's intranet, localinternets, the global-based Internet (including the World Wide Web(WWW)), virtual private networks, or the like. Backbone network 110supports wired, wireless, or both transmission media, includingsatellite, terrestrial (e.g., fiber optic, copper, twisted pair,coaxial, hybrid fiber-coaxial (HFC), or the like), radio, microwave,free-space optic, and/or any other form or method of transmission.

[0056] As such, OLT 102 utilizes backbone network 110 to communicatewith another device or application external to EPON 100. The device orapplication can be a server, web browser, operating system, other typesof information processing software (such as, word processing,spreadsheets, financial management, or the like), television or radiotransmitter, a component of another optical network, or the like.

[0057] III. Overview of PON Tagging

[0058] The present invention provides a tagging mechanism to identifythe origin ON 106 (i.e., the ON 106 that originates the frames passedwithin a PON segment). In an embodiment, a “PON tag type” field and a“PON tag control information” field (discussed with reference to “222”and “224”, respectively, in FIG. 2c, below) are produced and/oractivated to carry ONU identification information. This embodiment ofthe present invention enables the PON tag control information field andPON tag type field to propagate beyond the physical layer, such that thePON tag is available at the desired layer within ON 106 (and OLT 102).Thus, the present invention avoids replicas of protocol stacks since thePON tag is not necessarily placed in the preamble of a frame.

[0059] The tagging mechanism of the present invention is discussed withreference to FIGS. 2a-2 g, which illustrate several embodiments of aframe that can be transported within EPON 100. First, FIG. 2a shows aframe 200 a that does not include a tag. FIG. 2b shows a frame 200 bthat includes frame format extensions that support virtual local areanetwork (VLAN) tagging on Ethernet networks. FIG. 2c shows a frame 200 cthat includes frame format extensions to support PON tagging for anEPON. FIG. 2d and FIG. 2e show two embodiments (i.e., frame 200 d and200 e, respectively) that include both frame format extensions for VLANtagging and PON tagging. Finally, FIG. 2f and FIG. 2g show embodiments(i.e., frame 200 f and 200 g, respectively) that include a combinedframe format extension for VLAN tagging and PON tagging. As described ingreater detail, below, the present invention accommodates and processesall of the above-discussed tag types, in addition to any other type offrame presently known, or developed in the future, to be formatted fortransport over a PON segment.

[0060] Referring to FIG. 2a, frame 200 a begins with a “preamble” field(Pre) 202. Pre field 202 gives a recipient node (e.g., OLT 102 or ON106) time to recognize the presence of a signal before the frame data(shown as “data” field 212) arrives. Pre field 202 enables a recipientnode to lock onto the signal, and synchronize the recipient node's clockwith the transmitting node's clock. Following Pre field 202 is a “startof frame delimiter” (SFD) field 204. SFD field 204 demarcates thebeginning of relevant MAC frame information.

[0061] The first item of relevant MAC frame information is a“destination address” (DA) field 206. DA field 206 identifies one ormore network components designated to receive frame 200 a. The networkcomponent is typically customer premise equipment (CPE) associated withan ON 106. DA field 206 can be an individual address for a singlenetwork component/node, a multicast address for a group of networkcomponent/nodes, or a broadcast address for all available networkcomponent/nodes.

[0062] Frame 200 a also contains a “source address” (SA) field 208 thatidentifies a network component that originated the frame. As discussed,the network component is typically CPE associated with an ON 106.

[0063] A “length/type” field 210 is also included to specify thequantity of bytes present in data field 212. Data field 212 contains theMAC data unit. Finally, a “frame check sequence” (FCS) field 214supports error checking. In an embodiment, a cyclical redundancy check(CRC) value is calculated when frame 200 a is assembled. The CRC valueis appended at the end of frame 200 a in FCS field 214. Upon receipt, arecipient node performs identical checking and compares its result withthe CRC value. If no match is found, frame 200 a is discarded or flaggedas having an error.

[0064] Referring to FIG. 2b, frame 200 b includes frame formatextensions that support VLAN tagging on Ethernet networks. This formatis defined in IEEE standard 802.3ac for VLAN tagging, and IEEE standard802.1Q for the VLAN protocol. As shown, VLAN-tagged frame 200 b includesan identifier, or tag, that identifies the specific VLAN to which theframe belongs. The VLAN tag is shown as “VLAN tag type” field 216 and“VLAN tag control information” field 218, and is inserted between SAfield 208 and length/type field 210. VLAN tag type field 216 indicatesthe presence of a VLAN tag, and informs the recipient node thatlength/type field 210 can be located at an offset of four bytes furtherinto frame 200 b. The value “81-00” represents the IEEE EtherType fieldassigned for use with the IEEE standard 802.1Q. VLAN tag controlinformation field 218 contains the VLAN identifier (VID) which uniquelyidentifies the VLAN to which the Ethernet frame 200 b belongs. VLAN tagcontrol information field 218 also includes other information such as, auser priority field and a canonical format indicator (CFI), as definedin IEEE standard 802.1Q.

[0065] Frame 200 b also includes a “PAD” field 220. PAD field 220 isoptional and used to ensure that frame 200 b satisfies minimum allowablesize requirements. PAD field 220 is inserted and used to mitigatecollision with another frame if frame 200 b is too short. Inembodiments, PAD field 220 can also be included in frame 200 a,discussed above.

[0066] Referring to FIG. 2c, frame 200 c shows frame format extensionsfor supporting PON tagging within an EPON. The PON-tagged frame 200 cincludes a “PON tag type” field 222 and a “PON tag control information”field 224, which are referred to herein collectively as a “PON tag.” PONtag type field 222 is a two-byte field used to designate the presence ofa PON tag within frame 200 c. An IEEE EtherType field value can also beassigned for use with PON tag type 222. PON tag control informationfield 224 contains the control information for a specific ON 106.

[0067] In an embodiment, the control information includes an identifier(ON_ID) that uniquely identifies the origin ON 106. In an embodiment,one or more ON_IDs are assigned to each ON 106 by OLT 102. In anembodiment, the ON_ID is an address for one or more physical or logicalports at the physical interface of ON 106 to the PON segment. In anotherembodiment, the ON_ID is an address for one or more physical or logicalports at ON 106 that serves as the interface with one or more MACclients or subscribers end users. In another embodiment, a separateON_ID is assigned for the address at each port if multiple physicaland/or logical ports are configured at ON 106.

[0068] Other control information located in PON tag control informationfield 224 includes priority data, etc. The length of PON tag controlinformation field 224 is approximately 2 bytes, but can be smaller orlarger if required.

[0069] In an embodiment, additional fields are added to the PON tag(i.e., PON tag type field 222 and PON tag control information field 224)to support additional services (such as, security) on an Ethernetnetwork. As with frame 200 b, frame 200 c also includes PAD field 220 toensure that the minimum allowable size requirements are satisfied.

[0070] Another embodiment of a PON-tagged frame (i.e., frame 200 d) isshown in FIG. 2d. Frame 200 d includes frame format extensions thatsupport both VLAN tagging and PON tagging, and is therefore referred toas being a double tagged frame 200 d. As shown, VLAN tag type field 216and VLAN tag control information field 218 follow SA field 208.Thereafter, PON tag type field 222 and PON tag control information field224 are positioned before length/type field 210. Accordingly, frame 200d provides control information for passing an Ethernet frame within aVLAN as well as a PON segment.

[0071] The positions of the VLAN tag and PON tag are not necessarilyorder dependent. Hence, FIG. 2e shows another embodiment of a doubletagged frame 200 e. In frame 200 e, the PON tag type field 222 and PONtag control information field 224 precede the VLAN tag (i.e., 216 and218). In another embodiment (not shown), the tag type fields (i.e., 216and 222) are positioned adjacent to each other and precede the controlinformation fields (i.e., 218 and 224), or vice versa.

[0072]FIG. 2f. illustrates another embodiment of a PON-tagged frame(i.e., frame 200 f). In this embodiment, the VLAN and PON tag typefields (i.e., 216 and 222) are represented as a single combined tagspecification, shown as a single combined tag type field 226. Combinedtag type field 226 designates the presence of a VLAN tag, PON tag, orboth. The control information for the VLAN tag and PON tag is providedin VLAN tag control information field 218 and PON tag controlinformation field 224. Therefore, frame 200 f enables an Ethernet frameto be passed within a VLAN and/or PON segment depending on the contentsof fields 226, 218 and 224.

[0073] As previously discussed, the positions of the VLAN tag and PONtag are not necessarily order dependent. Hence as shown in FIG. 2g,combined tagged frame 200 g shows PON tag control information field 224preceding VLAN tag control information field 218. In another embodiment(not shown), VLAN tag control information field 218 and/or PON tagcontrol information field 224 precedes combined tag type field 226.

[0074] An embodiment of PON tag control information field 224 isillustrated in FIG. 3a. As shown, PON tag control information field 224includes a “filtering operation” (Op) field 302, a “mode” field 304, anda “tag identifier” (TID) field 306. TID field 306 contains an ON_ID asdiscussed above with reference to FIG. 2c. Mode field 304 specifieswhether, for example, frame 200 c is to be, or has been, transportedover a point-to-point communications path (i.e., P2P mode), or a sharedcommunications path (i.e., shared mode). Op field 302 specifies whether,for example, frame 200 c is to be filtered by a source identifier ordestination identifier. The source identifier refers to the origin ON106, and the destination identifier refers to a designated recipient(s)ON 106. The source identifier and/or destination identifier arespecified in TID field 306.

[0075] In an embodiment, OP field 302 and mode field 304 overlap infunctionality and, thus, is reduced to only one field. FIG. 3b shows anembodiment of PON tag control information field 224 that illustrates theoverlapping functionality. As shown, Op field 302 has been eliminated.Mode field 304 specifies the transport mode as being P2P or shareddistribution. As described in greater detail below, if mode field 304 isdesignated as P2P, the frame (e.g., frame 200 c) is filtered by adestination identifier. Otherwise, the frame is filtered by a sourceidentifier.

[0076] Hence, the PON tag of the present invention can be the ON_ID ofthe origin ON 106 or a derivative of the ON_ID value. In an embodiment,the PON tag contains additional fields for security and/or otherservices in addition to the forwarding fields described with referenceto FIG. 3a and FIG. 3b. Moreover, as described above, the tag typeinformation of the present invention is carried in a type field (i.e.,PON tag type field 222) that is similar to, but distinguishable from, aVLAN tag (i.e., tag type field 216). However, in another embodiment, PONtagging information is carried in a preamble (e.g., Pre field 202). Inother embodiments, the PON tagging information is positioned before DAfield 206, between DA field 206 and SA field 208, or at other locationswithin the tagged MAC frame.

[0077] IV. Operational Flow for Optical Node PON Tag Construction

[0078] As described above, the present invention implements a taggingmechanism for tracking the origin and/or destination of a frame within aPON segment, such as the PON segment shown in FIG. 1. Referring to FIG.4, flowchart 400 represents the general operational flow of anembodiment of the present invention. More specifically, flowchart 400shows an example of a control flow for producing and/or updating a PONtag at an origin ON 106.

[0079] The control flow of flowchart 400 begins at step 401 and passesimmediately to step 403. At step 403, an optical node (such as, ON 106)accesses information to be formatted and transmitted upstream to an OLT(such as, OLT 102). The information primarily comprises MAC clientinformation that includes information from a subscriber end user (asshown in FIG. 1), which includes data, voice, and/or video. The MACclient information can also include control messages generated at theoptical node (e.g., ON 106). For example, the control message can be arequest to OLT 102 for additional bandwidth.

[0080] The information is packetized, if it is not already, into aservice data unit. The optical node (e.g., ON 106) prepares a data frame(such as, for example, frame 200 c described above with reference toFIG. 2c). The data frame (e.g., frame 200 c) includes the service dataunit in data field 212.

[0081] At step 406, a PON tag (also referred to as “Ptag”) is producedand/or activated. For example referring back to the embodiment describedwith reference to FIG. 2c, PON tag type field 222 is added to the dataframe (e.g., frame 200 c) to designate the presence of a PON tag.Additionally, PON tag control information field 224 is added to specifythe PON tag control information, namely the origin ON_ID. As describedwith reference to TID field 306 in FIG. 3a, the ON_ID can be the addressfor the port (logical or physical) that the origin ON_ID utilizes totransmit the PON-tagged frame. Alternatively, the ON_ID can be theaddress for the port that ON_ID utilizes to service a subscriber enduser or MAC client associated with the PON-tagged frame. Thus, in anembodiment, the present invention implements a tagging mechanism thatonly specifies the origin ON_ID. In another embodiment (describedbelow), the tagging mechanism can also specify a destination ON_ID.Accordingly, the tagging mechanism of the present invention can specifythe origin ON_ID, a destination ON_ID, or both.

[0082] After the data frame has been assembled into PON tagged frame(e.g., frame 200 c), the control flow passes to step 409. At step 409,the PON-tagged frame is transmitted upstream to, for example, OLT 102.When transmitted in the upstream, the PON tag is referred to as anupstream PON tag (or Utag).

[0083] At step 412, a check is made for the presence of additionalinformation to be transmitted upstream. If additional information ispresent, the control flow returns to step 403. Otherwise, the controlflow ends as indicated at step 495.

[0084] V. Processing Upstream PON Tag by OLT

[0085] The control flow of FIG. 4 describes an exemplary taggingsolution for marking a frame to designate its origin optical node (e.g.,ON 106). As the frame is transported within a PON segment, a recipientcan easily identify the origin of the frame. Referring to FIG. 5,flowchart 500 represents the general operational flow of anotherembodiment of the present invention. More specifically, flowchart 500shows an example of a control flow for processing and/or updating a PONtag at an OLT (e.g., OLT 102) prior to passing the frame having the PONtag to a forwarding entity.

[0086] The control flow of flowchart 500 begins at step 501 and passesimmediately to step 503. At step 503, an OLT (e.g., OLT 102) receives anupstream frame from the PON segment. The upstream frame is one of theembodiments of PON-tagged frames described above (i.e., frame 200 c,frame 200 d, frame 200 e, frame 200 f, or frame 200 g of FIGS. 2c-2 g ).

[0087] The physical interface to OLT 102 supports P2P and/or sharedcommunications. Conventionally, a PON segment is neither a P2P segmentnor a shared segment. However, as described in greater detail below withreference to FIG. 9, the present invention enables an OLT (such as, OLT102) to configure and/or reconfigure its PON segment to emulate a P2Pservice, downstream broadcast service, shared service, or anycombination of the above. In an embodiment, OLT 102 includes a physicalport that is adaptable to be designated as a P2P and/or shared port. Inanother embodiment, OLT 102 includes a single physical port that can beconfigured and/or reconfigured into multiple logical or virtual ports.

[0088] In other words, although the physical transmission medium (e.g.,a fiber optic cable, free space optical link, etc.) is coupled to asingle physical input/output port of OLT 102, OLT 102 or systemcomponents associated with OLT 102 are enabled to parse and/or processthe information exchanged via the single physical port as if theinformation is being exchanged over separate physical ports. Byarbitrating bandwidth among the plurality of ON 106 with respect totime, frequency, code, and/or the like, OLT 102 can create a pluralityof upstream and/or downstream channels. Although these channels share acommon physical port at OLT 102, the information exchanged over thesingle physical port is parsed and/or processed according to thedesignated channel (e.g., a channel identifier in the header of anupstream frame). Assigning each channel to a designated logical orvirtual port, OLT 102 is enabled to operate as if the information isbeing exchanged over different channels, with each channel being treatedas if it is being serviced over a dedicated logical port at OLT 102. Assuch, the physical interface to OLT 102 includes, in embodiments, one ormore virtual/logical ports for P2P service, one or more virtual/logicalports for shared service, or a combination of both.

[0089] If a port (physical or logical) receives a PON-tagged frame fromON 106, the port is referred to as being part of a PON-enabled (ortag-enabled) physical interface because the port is linked to an opticalelement capable of producing and/or passing frames that are taggedaccording to the present invention. If a port (physical or logical)exclusively receives frames lacking a PON tag, the port is referred toas being part of a traditional physical interface because the port isnot linked to an optical element capable of producing and/or passingframes that are tagged according to the present invention. It should beunderstood the expression “PON-enabled,” as used herein, is not intendedto be limited to passive optical networks. As previously discussed inalternate embodiments, the present invention can be implemented in othertypes of networks.

[0090] Accordingly, in an embodiment, OLT 102 is configured to receiveand/or transmit frames only on a PON-enabled physical interface. Inanother embodiment, OLT 102 is configured to receive frames and/ortransmit from a traditional physical interface and a PON-enabledphysical interface. In an embodiment, OLT 102 includes an interface tobackbone 110, which is not a PON-enabled interface, and at least onePON-enabled interface. A frame coming from the “non-PON-enabled”interface to backbone 110 is referred to as an external frame. A framearriving from the PON-enabled interface is referred to as an internalframe. All internal frames in a PON segment are PON-tagged frames.External frames are not PON-tagged frames.

[0091] At step 506, the OLT (e.g., OLT 102) detects or searches for thepresence of a PON tag. Referring back to FIGS. 2c-2 g in an embodiment,a PON tag type field 222 is included to designate the presence of a PONtag. Thus, if PON tag type field 222 is found, the frame is determinedto be a PON-tagged frame (e.g., frame 200 c). The control flow wouldthen pass to step 509.

[0092] Otherwise, if no PON tag is detected, the frame is determined tobe a non-PON-tagged frame (such as, frame 200 a or 200 b). The frame isconsidered to have originated external to the PON segment or from anon-PON enabled port. Therefore, the control flow would pass to step512. In an embodiment, if the PON tag (e.g., PON tag control informationfield 224) for a PON-tagged frame (e.g., frame 200 c) is missing, lost,or damaged, the OLT (e.g., OLT 102) discards the frame if it goes to thesame PON interface, or treats the frame as a non-PON-tagged frame if itgoes to an external interface.

[0093] At step 509, the OLT (e.g., OLT 102) extracts or derives the PONtag value from PON tag control information field 224. This value is usedto prepare a forwarding tag (or Ftag) that is appended to frame 200 c.In an embodiment, the forwarding tag is the upstream PON tag. In anotherembodiment, the forwarding tag is identical to the ON_ID specified inthe PON tag. In another embodiment, the forwarding tag is a derivativeof any information in the upstream PON tag. In another embodiment, theforwarding tag is derived from any information in the original frame(including the upstream PON tag), or additional state in OLT 102.

[0094] At step 512, the OLT (e.g., OLT 102) constructs a PON tag for anon-PON-tagged frame. However since the origin optical node (e.g., ON106) is unknown or the origin node is external to the destination PONsegment, the ON_ID is set to a null value to thereby produce a “null PONtag.” In an embodiment, a universal identifier (i.e., “universal ON_ID”)is specified for all broadcast or multicast operations. This universalidentifier is also used as the null PON tag value. The null PON tagvalue is used, at step 512, to prepare a forwarding tag that is appendedto the frame. As intimated, the forwarding tag can be identical to, or aderivative of, the null ON_ID value. For example, referring back to FIG.3b , the mode field 304 can be set to shared distribution or P2P. If theframe is being sent to an optical node (e.g., ON 106) having a P2Pcommunications link with the OLT (e.g., OLT 102), the TID field 306 isset to the ON_ID for the destination ON 106, and the mode is set to P2P.Thus, the PON tag would have mode field 304 and TID field 306 values of“(P2P, destination ON_ID).” If, however, the frame is being sent anoptical node (e.g., ON 106) operating on a shared communications pathwith the OLT (e.g., OLT 102) (or if mode is unknown), the mode field 304and TID field 306 values would read as “(shared, universal ON_ID).”

[0095] It should be understood that a multicast or broadcast frame canbe sent on a P2P path to each member of the multicast or broadcastgroup, or on a shared path to all optical nodes (e.g., ON 106) operatingon the shared path. If sent to all optical nodes operating on a sharedpath, the optical nodes that are members of the multicast group wouldaccept the frame, and the non-members would reject the frame. Similarly,it should be understood that a unicast frame can be sent on a P2P pathto the designated optical node (e.g., ON 106), or on a shared path toall optical nodes (e.g., ON 106) operating on the shared path. If sentto all optical nodes operating on a shared path, the designatedrecipient of the unicast would accept the frame, and all other opticalnodes on the shared path would reject the frame.

[0096] At step 515, the forwarding-tagged frame is queued according tothe incoming port (i.e., physical port or logical port) of the physicalinterface that received the frame. In an embodiment, OLT 102 matches theincoming port to the frame upon receipt. In another embodiment, theincoming port is detected or extracted from one or more fields withinthe frame (e.g., from PON tag control information field 224). In anotherembodiment, OLT 102 has separate and parallel processing paths for allavailable ports, and queues the frames accordingly.

[0097] At step 518, the queues (designating a respective incoming port)are emptied to pass the upstream frames to a forwarding entity. In anembodiment based on logical ports, the upstream frames are passed withthe forwarding tags. In an embodiment based on multiple physical ports,the upstream frames are passed over designated physical interfaces withthe forwarding entity. After the upstream frames are passed to theforwarding entity, the control flow ends as indicated by step 595.

[0098] Referring, now, to FIG. 6, flowchart 600 represents the generaloperational flow for processing and/or updating a PON tag fortransmission from an OLT (e.g., OLT 102), according to an embodiment ofthe present invention. More specifically, flowchart 600 shows an exampleof a control flow for processing and/or updating a PON tag after beingpassed to a forwarding entity associated with an OLT (e.g., OLT 102).

[0099] The control flow of flowchart 600 begins at step 601 and passesimmediately to step 603. At step 603, the forwarding entity receives aframe. In an embodiment based on logical ports, the frame includes theforwarding tag. In an embodiment based on multiple physical ports, theforwarding entity notes the incoming port that received the frame, sincethe frames are queued by incoming port.

[0100] At step 606, the forwarding entity determines the destinationport(s) for the frame. In an embodiment, the forwarding entity uses thedestination address (i.e., DA field 206) to query a look-up orforwarding table to determine the destination port(s). The table can beprogrammable to learn destination addresses and corresponding port(s).

[0101] At step 609, the forwarding entity considers the frame's incomingport type (i.e., a traditional physical interface or a PON-enabledphysical interface). As discussed, this information is noted at step 603from the queue. In an embodiment, the forwarding entity learns that aspecific queue is associated with a specific port type. In anotherembodiment, a tag is appended to the frame to designate the incomingport prior to being handed to the forwarding entity, and the forwardingentity learns the port type. Alternatively, a tag can be appended, priorto delivering the frame to the forwarding entity, to designate theincoming port type. In another embodiment, a learning table is queriedand/or updated to determine the port type from the incoming port. Aswould be apparent to one skilled in the relevant art(s), other variants,methodologies, or techniques can be used to permit the forwarding entityto become aware of the incoming port or port type.

[0102] If the incoming port is PON-enabled, at step 612, the incomingport is included as a destination port, regardless of whether it hadbeen determined to be a destination port at step 606. As a result, aPON-tagged frame is always reflected back to the origin ON 106. In anembodiment, all upstream traffic is reflected back on all PON-enabledports. In another embodiment, upstream traffic is only reflected back ona PON-enabled port configured for shared distributions.

[0103] On the other hand, if the incoming port is a traditional port,the control flow passes immediately to step 615. Therefore, since aforwarding entity conventionally does not transmit signals back on anincoming port, the frame is not returned to the incoming port if it isnot included in the destination port(s).

[0104] At step 615, the frame is queued according to its destinationport(s). The queues are subsequently emptied for further processing. Ifa destination port is a PON-enabled port, the OLT (e.g., OLT 102)verifies or prepares a PON tag for downstream transmission. In thedownstream, the PON tag is referred to as the downstream PON tag (orDtag).

[0105] Referring back to FIG. 3b, a representative PON tag includes modefield 304 denoted as “shared” or “P2P,” and TID field 306 specifying anorigin ON_ID. If mode field 304 is set to “P2P,” the forwarding entitydetermines the PON segment destination and OLT 102 modifies, ifnecessary, TID field 306 to specify the “destination” ON_ID. Themodified tag “(P2P, destination ON_ID)” becomes the downstream PON tagthat is passed with the frame to its downstream destination. Asdiscussed above if the frame is externally generated or from an unknownsource, the PON tag would already read “(P2P, destination ON_ID).”Therefore, no modification should be required.

[0106] On the other hand if mode field 304 is set to “shared,” theforwarding entity determines the group membership for the multicast orbroadcast, but OLT 102 does not modify the TID field 306. The downstreamPON tag is the same as the upstream PON tag, namely “(shared, originON_ID)” if the frame is PON-originated or “(shared, universal ON_ID)” ifexternally generated or from an unknown source.

[0107] If a destination port is a traditional port or if the frame isbeing sent to a higher layer application or MAC client of the OLT (e.g.,OLT 102), the PON tag is removed. Moreover if at any step a PON-taggedframe is passed to a traditional device (e.g., bridge, router, etc.)that is not PON-aware, the PON tag is eliminated. After the frame hasbeen passed to its destination port(s), the control flow ends asindicated by step 695.

[0108] The present invention, therefore, provides a PON-aware forwardingentity having the capability to interact with a PON segment as if thesegment is one of the known segment types, namely shared, P2P, or both.Unlike a conventional forwarding entity, the PON-aware forwarding entityof the present invention does not assume all peers have seen an upstreamframe. A conventional forwarding entity will not hand a frame to adestination port if it is the incoming port that received the frame.However, in the present invention, a PON-aware forwarding entityreflects back all PON-tagged frames received over a shared path.

[0109] VI. Processing Downstream PON Tag by an Optical Node

[0110] As discussed, FIG. 4 describes an embodiment for producing and/orupdating a PON tag for upstream transmissions. FIGS. 5-6 describeembodiments for processing and/or updating a PON tag at an OLT (e.g.,OLT 102). Referring, now, to FIG. 7, flowchart 700 represents thegeneral operational flow of the reception process at an optical node(e.g., ON 106) according to an embodiment of the present invention. Morespecifically, flowchart 700 shows an example of a control flow forprocessing and/or updating a PON tag upon delivery at an optical node(e.g., ON 106).

[0111] The control flow of flowchart 700 begins at step 701 and passesimmediately to step 703. At step 703, an optical node (e.g., ON 106)receives a frame (e.g., frame 200 c, 200 d, 200 e, etc.) from adownstream channel. At step 706, the optical node (e.g., ON 106) detectsor reads a PON tag appended to the frame. As discussed, in anembodiment, PON tag type field 222 designates the frame as being aPON-tagged frame.

[0112] At step 709, the optical node (e.g., ON 106) determines whetherthe frame has been distributed in P2P or shared mode. In an embodiment,mode field 304 is processed to determine whether the frame is designatedas being in P2P or shared mode. If P2P mode is determined, the controlflow passes to step 712. Otherwise, the control flow passes to step 715for processing shared distributions.

[0113] At step 712, the optical node (e.g., ON 106) determines whetherit is the intended recipient of the frame. As discussed above, aPON-tagged frame sent downstream in P2P mode includes mode field 304 andTID field 306 values reading “(P2P, destination ON_ID). If thedestination ON_ID specified in TID field 306 does not match the ON_ID ofthe recipient optical node (e.g., ON 106), the optical node is not theintended recipient. As such, the frame is discarded at step 718.Otherwise, the frame is accepted at step 721.

[0114] Shared mode distributions are processed at step 715. Whenexecuted, step 715 enables a recipient optical node (e.g., ON 106) todetermine whether it originated a PON-tagged frame (e.g., frame 200 c,200 d, 200 e, etc.) received in the downstream. As discussed above, aPON-tagged frame sent on a shared downstream includes mode field 304 andTID field 306 values reading “(shared, origin ON_ID)” for PON-originatedframes and “(shared, universal ON_ID)” for externally generated orunknown sourced frames. Processing TID field 306, the optical node(e.g., ON 106) determines if its ON_ID(s) matches and hence, whether itis the origin optical node (i.e., it originated the PON-tagged frame).If the recipient optical node is the origin optical node, the frame isrejected at step 718. Otherwise, it is accepted, at step 721, becausethe frame is determined to be produced by a peer optical node (e.g., ON106).

[0115] This process is effective for supporting reflect-back operationsof a PON-enabled OLT (e.g., OLT 102). The reflect-back operations permitone or more peer optical nodes (e.g., ON 106) to remain aware of signalstransmitted upstream to the OLT (e.g., OLT 102), especially on a sharedcommunications path. Additionally, reflecting-back permits a peeroptical node on a shared path to receive the frame if an intendeddestination is one of the subscriber end users of the peer optical node.Conversely, traditional OLT-forwarding entities do not return the frameto the shared path peers because it assumes that the peers have alreadyseen the frame.

[0116] If the frame (received from a shared or P2P path) is accepted,then at step 724, the PON tag is deactivated or removed from the frameand sent to a higher layer application or MAC client for furtherprocessing. Afterwards, the control flow ends as indicated by step 795.

[0117] As described above, TID field 306 designates the ON_ID as being asingle node identifier. In other words, TID field 306 specifies anidentifier for a single optical element of system 100 (namely, one of ON106). It should be understood that the single node designation of TIDfield 306 has been described by way of example. In embodiments of thepresent invention, the contents or value of TID field 306 is easilyextendable to support a multi-node designation. If, for example, asingle ON 106 belongs to one or more groups of ON 106, a membershipidentifier is specified for each group. The single ON 106, therefore,retains a list of membership identifiers for each of these groups. As aframe is processed as described herein, a membership identifier isincluded in TID field 306 to specify source and/or destinationidentifiers for a multicast according to the embodiments hereindescribed. For example, ON 106 is enabled to perform a check rule toeither select a membership identifier to produce a PON tag prior tosending a frame, or to verify a membership identifier to process a PONtag prior to accepting or rejecting a frame. Similarly, OLT 102 isenabled to perform a check rule to select a membership identifier whileprocessing or producing a downstream PON tag, as discussed above.

[0118] VII. System Architecture for ONU and OLT

[0119]FIG. 8 illustrates an embodiment of ON 106 that can be used toimplement the present invention as described with reference to FIGS.1-7. ON 106 includes a physical layer interface (PHY) 802, media accesscontrol (MAC) layer 804, and MAC control layer 806. In an embodiment,PHY 802, MAC 804, and MAC control 806 are configured to comply with thespecifications of IEEE standard 802.3 and/or 803.3ah.

[0120] PHY 802 serves to receive and transmit signals (e.g., voice,data, video, etc.) among the subscriber end-users (shown as MAC client808), as discussed above with reference to FIG. 1. As discussed above,ON 106 utilizes one or more physical or logical ports to communicatewith OLT 102 over the PON segment. Additionally, one or more physical orlogical ports are used to communicate with its end users (MAC client808). PHY 802 also supports full duplex communications (e.g., voice,data, video, control messages) with OLT 102. Hence, PHY 802 isconfigurable to support electronic, electromagnetic, optical signals,and/or the like. PHY 802 modulates signals to be transmitted as bursts,and demodulates signals that it receives. In an embodiment, PHY 802performs error checking on a received signal and/or discard the signalif errors are found.

[0121] Signals from PHY 802 are passed to MAC 804 for Ethernet protocolprocessing. It should be understood that the above reference to Ethernetprotocol processing is provided by way of example. Hence, in alternateembodiments, MAC 804 performs protocol processing in compliance withother types of communication protocols governing multimedia distributionnetworks.

[0122] MAC control 806 receives frames from MAC 804 and integrates thetagging mechanism of the present invention. In an embodiment, MAC 804takes a frame coming from MAC client 808, and appends or inserts a PONtag (e.g., PON tag type field 222 and PON tag control information field224). The resulting PON tagged-frame (e.g., frame 200 c, 200 d, 200 e,etc.) is queued for delivery to PHY 802.

[0123] During registration with OLT 102, ON 106 receives instructions(e.g., ON_ID and/or membership identifier values to use in the PON tag)to establish and format the ports. At this time, ON 106 can requestadditional ports.

[0124]FIG. 9 illustrates an OLT 102 according to an embodiment of thepresent invention. OLT 102 includes a physical layer interface (PHY)902, media access control (MAC) layer 904, MAC control layer 906, aforwarding entity 908, and a forwarding table 914. In an embodiment, PHY902, MAC 904, and MAC control 906 are configured to comply with therequirements of IEEE standard 802.3, and forwarding entity 908 isconfigured to conform to IEEE standard 802.1D, with additionalfunctionality according to the present invention.

[0125] PHY 902 supports full duplex communications (e.g., voice, data,video, control messages) with ON 106 (or ONU 800). Accordingly, PHY 902transmits and receives optical signals via the PON segment. PHY 902demodulates the signals to decompress and/or extract voice, data, video,requests, other control messages, and/or the like. In an embodiment, PHY902 performs error checking, if required. If errors are detected, theburst is discarded. In another embodiment, the burst is flagged and theerror is corrected at MAC 904.

[0126] Therefore, MAC 904 performs Ethernet protocol processing. Asdiscussed above, it should be understood that the above reference toEthernet protocol processing is provided by way of example. Hence, inalternate embodiments, MAC 904 performs protocol processing incompliance with other types of communication protocols governingmultimedia distribution networks.

[0127] MAC control 906 processes, updates, and/or constructs the PON tagof the present invention. In an embodiment, MAC control 906 reads orextracts the PON tag received from PHY 902 and produced by the origin ON106, and prepares a forwarding tag, as described above. If MAC control906 receives a frame lacking a PON tag (e.g., an external frame), a nullPON tag is constructed, as described above. The null PON tag is appendedto the frame as its forwarding tag. The frame (with forwarding tag) isqueued according to the incoming port that received the frame from theupstream.

[0128] Forwarding entity 908 (such as a bridge, router, etc.) readsdestination address (e.g., DA field 206) and queries forwarding table914 to determine the destination port(s) for each frame. Forwardingtable 914 includes disposition instructions for forwarding information(e.g., frame 200 a, 200 b, 200 c, 200 d, etc.) delivered to OLT 102. Thedisposition instructions include, but are not limited to, a destinationport (physical or logical) corresponding to a destination or sourceaddress, port mirror requirements, frame handling requirements,prioritization, multicast group membership, and/or like features. In anembodiment, forwarding table 914 is programmable to learn portassociations with MAC or PON addresses, and/or forwarding table 914 isresponsive to periodic or on-demand updates, regarding the portassociations, from an operator interface, software application, oranother control system. In an embodiment, forwarding table 914 isprogrammable to store a PON tag with the associated frame.

[0129] Upon receipt of disposition instructions, forwarding entity 908filters and queues the frames to be forwarded to the destinationport(s). Forwarding entity 908 is a PON-aware forwarding entity, andtherefore, forwarding entity 908 forwards back a frame to its incomingport if the incoming port is a PON port. Additionally, forwarding entity908 includes a plurality of physical or logical ports for downstreamtransmissions to ON 106. One or more shared physical or logical portssupport shared communications, and multiple physical or logical portssupport P2P communications. Each ON 106 has a designated physical orlogical port for P2P communications. Thus, in an embodiment OLT 102includes a single physical port to the PON segment, multiple logicalports configured for P2P and/or shared paths, and another physical portto backbone 110. In another embodiment, OLT 102 includes multiplephysical ports with or without logical ports.

[0130] After the frames have been filtered into the appropriatedestination port, the frames (with their appended forwarding PON tags)are forwarded to MAC control 906. MAC control 906 updates or prepares adownstream PON tag (or Dtag) for each frame. The frame then passes toMAC 904 for further formatting or protocol processing, and to PHY 902 tobe transmitted to its downstream destination.

[0131] VIII. Exemplary System Implementation

[0132] FIGS. 1-9 are conceptual illustrations allowing an easyexplanation of the present invention. It should be understood thatembodiments of the present invention could be implemented in hardware,firmware, software, or a combination thereof. In such an embodiment, thevarious components and steps would be implemented in hardware, firmware,and/or software to perform the functions of the present invention. Thatis, the same piece of hardware, firmware, or module of software couldperform one or more of the illustrated blocks (i.e., components orsteps).

[0133] Additionally, the present invention can be implemented in one ormore computer systems capable of carrying out the functionalitydescribed herein. Referring to FIG. 10, an example computer system 1000useful in implementing various components or steps of the presentinvention is shown. Various embodiments of the invention are describedin terms of this example computer system 1000. After reading thisdescription, it will become apparent to one skilled in the relevantart(s) how to implement the invention using other computer systemsand/or computer architectures.

[0134] The computer system 1000 includes one or more processors, such asprocessor 1004. Processor 1004 can be a special purpose or a generalpurpose digital signal processor. Processor 1004 is connected to acommunication infrastructure 1006 (e.g., a communications bus, crossoverbar, or network). Various software implementations are described interms of this exemplary computer system. After reading this description,it will become apparent to a one skilled in the relevant art(s) how toimplement the invention using other computer systems and/or computerarchitectures.

[0135] Computer system 1000 also includes a main memory 1008, preferablyrandom access memory (RAM), and can also include a secondary memory1010. The secondary memory 1010 can include, for example, a hard diskdrive 1012 and/or a removable storage drive 1014, representing a floppydisk drive, a magnetic tape drive, an optical disk drive, etc. Theremovable storage drive 1014 reads from and/or writes to a removablestorage unit 1018 in a well-known manner. Removable storage unit 1018represents a floppy disk, magnetic tape, optical disk, etc. As will beappreciated, the removable storage unit 1018 includes a computer usablestorage medium having stored therein computer software (e.g., programsor other instructions) and/or data.

[0136] In alternative implementations, secondary memory 1010 includesother similar means for allowing computer software and/or data to beloaded into computer system 1000. Such means include, for example, aremovable storage unit 1022 and an interface 1020. Examples of suchmeans include a program cartridge and cartridge interface (such as thatfound in video game devices), a removable memory chip (such as, an EPROMor PROM) and associated socket, and other removable storage units 1022and interfaces 1020 which allow software and data to be transferred fromthe removable storage unit 1022 to computer system 1000.

[0137] Computer system 1000 can also include a communications interface1024. Communications interface 1024 allows software and/or data to betransferred between computer system 1000 and external devices. Examplesof communications interface 1024 include a modem, a network interface(such as an Ethernet card), a communications port, a PCMCIA slot andcard, etc. Software and data transferred via communications interface1024 are in the form of signals 1028 which can be electronic,electromagnetic, optical, or other signals capable of being received bycommunications interface 1024. These signals 1028 are provided tocommunications interface 1024 via a communications path (i.e., channel)1026. Communications path 1026 carries signals 1028 and can beimplemented using wire or cable, fiber optics, a phone line, a cellularphone link, an RF link, free-space optics, and/or other communicationschannels.

[0138] In this document, the terms “computer program medium” and“computer usable medium” are used to generally refer to media such asremovable storage unit 1018, removable storage unit 1022, a hard diskinstalled in hard disk drive 1012, and signals 1028. These computerprogram products are means for providing software to computer system1000. The invention, in an embodiment, is directed to such computerprogram products.

[0139] Computer programs (also called computer control logic or computerreadable program code) are stored in main memory 1008 and/or secondarymemory 1010. Computer programs can also be received via communicationsinterface 1024. Such computer programs, when executed, enable thecomputer system 1000 to implement the present invention as discussedherein. In particular, the computer programs, when executed, enable theprocessor 1004 to implement the processes of the present invention, suchas the method(s) implemented using components of OLT 102 and/or ON 106described above, such as various steps of methods 400, 500, 600, and/or700, for example. Accordingly, such computer programs representcontrollers of the computer system 1000.

[0140] In an embodiment where the invention is implemented usingsoftware, the software can be stored in a computer program product andloaded into computer system 1000 using removable storage drive 1014,hard drive 1012, interface 1020, or communications interface 1024. Thecontrol logic (software), when executed by the processor 1004, causesthe processor 1004 to perform the functions of the invention asdescribed herein.

[0141] In another embodiment, the invention is implemented primarily inhardware using, for example, hardware components such as applicationspecific integrated circuits (ASICs). Implementation of the hardwarestate machine so as to perform the functions described herein will beapparent to one skilled in the relevant art(s).

[0142] In yet another embodiment, the invention is implemented using acombination of both hardware and software.

[0143] While various embodiments of the present invention have beendescribed above, it should be understood that they have been presentedby way of example, and not limitation. It will be apparent to oneskilled in the relevant art(s) that various changes in form and detailcan be made therein without departing from the spirit and scope of theinvention. Moreover, it should be understood that the method, system,and computer program product of the present invention could beimplemented in any multi-nodal communications environment governed bycentralized nodes. The nodes include, but are not limited to, cablemodems and headends, as well as communication gateways, switches,routers, Internet access facilities, servers, personal computers,enhanced telephones, personal digital assistants (PDA), televisions,set-top boxes, or the like. Thus, the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

What is claimed is:
 1. A method for filtering and forwarding informationin an optical network, comprising the steps of: accessing a framecarrying client information from an incoming port in communications withone or more optical elements of the optical network; detecting apresence or absence of an optics control tag integrated with said frame;determining a distribution mode for said frame; passing said frame withsaid optics control tag to one or more destination ports forcommunicating with one or more corresponding destination addresses forsaid frame, wherein said passing step includes passing said frame withsaid optics control tag to said incoming port in response to determiningsaid distribution mode being designated for a shared service; andforwarding said frame with said optics control tag from said one or moredestination ports to said one or more corresponding destinationaddresses, whereby said frame with said optics control tag isreflected-back from said incoming port in response to said determining ashared service.
 2. The method of claim 1, further comprising the stepsof: constructing a null tag in response to detecting the absence of saidoptics control tag; and integrating said null tag with said frame tothereby produce said optics control tag.
 3. The method of claim 2,further comprising the steps of: enabling said null tag to designatesaid distribution mode for a point-to-point service and to specify anidentifier for a designation optical element, in response to determiningsaid destination optical element is receiving point-to-point service;and enabling said null tag to designate said distribution mode for ashared service and to specify an universal identifier for a group ofdestination optical elements, in response to determining said frame isdesignated for delivery to an optical element receiving shared service.4. The method of claim 1, further comprising the step of: determiningsaid frame to include an optics control tag and a distribution modedesignated for a point-to-point service, whereby said frame is notreflected-back from said incoming port.
 5. The method of claim 1,further comprising the step of: passing said frame with said opticscontrol tag to a forwarding entity to determine said one or moredestination ports, wherein said forwarding entity decides whether topass said frame to said incoming port.
 6. The method of claim 1, furthercomprising the step of: querying a forwarding table to determine saidone or more corresponding destination addresses.
 7. The method of claim1, wherein said one or more corresponding destination addresses includean address for one of said one or more optical elements and/or anaddress for a MAC client coupled to one of said one or more opticalelements.
 8. The method of claim 1, wherein said determining adistribution mode step further comprises the step of: processing saidoptics control tag to determine said distribution mode, saiddistribution mode being designated for a point-to-point service or ashared service.
 9. The method of claim 1, wherein said determining adistribution mode step further comprises the step of: determining saiddistribution mode from a destination address.
 10. The method of claim 1,further comprising the step of: verifying and/or updating said opticscontrol tag prior to passing said frame to said one or more destinationports.
 11. The method of claim 10, further comprising the steps of:verifying and/or updating said optics control tag to specify anidentifier for a destination optical element, in response to determiningsaid distribution mode being designated for a point-to-point service;verifying and/or updating said optics control tag to specify anidentifier for a source optical element, in response to determining saiddistribution mode being designated for a shared service; and verifyingand/or updating said optics control tag to specify a universalidentifier for a group of destination optical elements, in response todetermining said frame as originating from an external or unknown sourceand determining said frame is not being sent to a single destinationoptical element.
 12. The method of claim 1, further comprising the stepsof: passing said frame to a destination port for communicating with adevice external to the optical network; and forwarding said framewithout said optics control tag to said device.
 13. A method forprocessing information from a downstream path of an optical network,comprising the steps of: accessing, at a recipient optical node, a framehaving an optics control tag embedded therein; determining adistribution mode for said frame; detecting an optical node identifierfrom said optics control tag; and accepting said frame in response todetecting said distribution mode being designated for a shared serviceand to detecting said optical node identifier not matching an opticalnode identifier assigned to said recipient optical node.
 14. The methodof claim 13, further comprising the step of: accepting said frame inresponse to detecting said distribution mode being designated for apoint-to-point service and to detecting said optical node identifiermatching an optical node identifier assigned to said recipient opticalnode.
 15. A system for forwarding frames in an optical network,comprising: upstream communications means for transmitting an opticalsignal carrying client information on a communications path designatedto emulate shared distributions in the optical network, wherein saidupstream communications means includes upstream tag control means forintegrating an optics control tag with said client information, whereinsaid optics control tag includes instructions for forwarding said clientinformation within the optical network; primary communications means formanaging communications with said upstream communications means, whereinsaid primary communications means includes primary tag control means fordetecting said optics control tag; and forwarding means for filteringand/or forwarding said client information according to said opticscontrol tag, wherein said forwarding means is responsive to receivingsaid client information from said primary communications means andadapted to reflect back said client information to said upstreamcommunications means on said communications path.
 16. The system ofclaim 15, wherein said communications path is designated to emulateshared distributions to optical elements receiving shared service. 17.The system of claim 15, wherein the optical network is a passive opticalnetwork.
 18. The system of claim 15, wherein said optical signalincludes an Ethernet-formatted frame carrying client information. 19.The system of claim 15, wherein said communications path is part of aHFC network.
 20. The system of claim 15, wherein said upstream tagcontrol means is a MAC Ethernet entity, said MAC Ethernet entityincluding a physical interface layer, a media access control layer, anda MAC control layer.
 21. The system of claim 15, wherein said primarytag control means is a MAC Ethernet entity, said MAC Ethernet entityincluding a physical interface layer, a media access control layer, anda MAC control layer.
 22. The system of claim 15, wherein said primarycommunications means includes a physical interface to saidcommunications path, wherein said physical interface includes at leastone physical port for transmitting and/or receiving said clientinformation.
 23. The system of claim 15, wherein said primarycommunications means includes a physical interface to said communicationpaths, wherein said physical interface includes at least one logicalport for transmitting and/or receiving said client information.
 24. Thesystem of claim 15, wherein said forwarding entity is a router.
 25. Thesystem of claim 15, wherein said forwarding entity is a bridge.
 26. Anoptical line terminal for managing the exchange of information within anoptical network, comprising: interfacing means for accessing clientinformation from a communications path designated to emulate shareddistributions in the optical network; an optics tag detector fordetecting a presence of an optics control tag integrated with saidclient information; and a forwarding entity for filtering and/orforwarding said client information according to said optics control tag,wherein said forwarding entity is adapted to reflect back said clientinformation on said communications path.
 27. The optical line terminalof claim 26, further comprising: a tag constructor for constructing anull optics control tag in response to said optics tag detector beingunable to detect the presence of an optics control tag.
 28. The opticalline terminal of claim 26, further comprising: a forwarding table fortracking disposition instructions, wherein said forwarding table returnsdisposition instructions to said forwarding entity in response toqueries regarding said client information.
 29. The optical line terminalof claim 28, wherein said forwarding table is programmable to learn anassociation of destination ports with destination addresses for saidclient information.
 30. The optical line terminal of claim 28, whereinsaid forwarding entity reflects back said client information in responseto said disposition instructions.
 31. The optical line terminal of claim28, further comprising: a tag constructor for updating said opticscontrol tag in response to said disposition instructions being returnedby said forwarding table.
 32. The optical line terminal of claim 28,wherein said interfacing means accesses information from at least onecommunications path designated to emulate point-to-point distributionsin the optical network, wherein said forwarding entity is responsive toforwarding information over said communications path designated for saidshared distributions and/or said communications path designated for saidpoint-to-point distributions.
 33. The optical line terminal of claim 32,wherein said communications path is designated to emulate shareddistributions to optical elements receiving shared service.
 34. Theoptical line terminal of claim 32, wherein said communications path isdesignated to emulate point-to-point distributions to an optical elementreceiving point-to-point service.
 35. The optical line terminal of claim32, wherein a physical interface of the optical line terminal to saidcommunications path includes at least one physical port.
 36. The opticalline terminal of claim 32, wherein a physical interface of the opticalline terminal to said communications path includes at least one logicalport.
 37. An optical network element for processing information from adownstream path of an optical network, comprising: interfacing means foraccessing a frame from a communications path of the optical network; anoptics tag detector for detecting a presence of an optics control tagappended to said frame, wherein said optics tag detector is responsiveto determining a distribution mode for said optics control tag, whereinsaid optics tag detector is responsive to detecting an optical nodeidentifier from said optics control tag; and a frame controller foraccepting said frame in response to said optics tag detector detectingsaid distribution mode being designated for a shared service and todetecting said optical node identifier not matching an optical nodeidentifier assigned to the optical network element.
 38. The method ofclaim 37, wherein said frame controller is responsive to accepting saidframe in response to said optics tag detector detecting saiddistribution mode being designated for a point-to-point service and todetecting said optical node identifier matching an optical nodeidentifier assigned to the optical network element.
 39. A method fortransporting a frame within an optical network, comprising the steps of:accessing a frame carrying client information; appending destinationinformation including instructions for delivering said frame to adestination; and appending optics control information to said frame,wherein said optics control information includes an identifier for anoriginating optical element that introduces said frame to the opticalnetwork, wherein said optics control information includes instructionsfor reflecting-back said frame to said originating optical element. 40.The method of claim 39, further comprising the step of: appending anoptics tag indicator for designating a presence of said optics controlinformation.
 41. The method of claim 39, further comprising the step of:appending network control information for identifying a virtual localarea network to which said frame belongs.
 42. The method of claim 41,further comprising the step of: appending a network tag indicator fordesignating a presence of said network control information.
 43. Themethod of claim 42, further comprising the step of: appending an opticstag indicator for designating a presence of said optics controlinformation.
 44. The method of claim 41, further comprising the step of:appending a tag indicator for designating a presence of said opticscontrol information and/or said network control information.
 45. Themethod of claim 39, wherein said optics control information includesinstructions for designating a mode for distributing said frame withinthe optical network, wherein said frame is reflected-back to saidoriginating optical element in response to said mode being designatedfor a shared service.
 46. A computer data signal embodied in a carrierwave, comprising: a first code segment carrying client information; asecond code segment including instructions for delivering said clientinformation to a destination; and a third code segment including opticscontrol information, wherein said third code segment includesidentification information for an originating optical element thatintroduces said client information to the optical network, wherein saidthird code segment includes instructions for reflecting-back said frameto said originating optical element.
 47. The computer data signalaccording to claim 46, further comprising: a fourth code segmentincluding information indicating a presence of said optics controlinformation.
 48. The computer data signal according to claim 46, furthercomprising: a fourth code segment including network control informationfor identifying a virtual local area network to which said clientinformation belongs.
 49. The computer data signal according to claim 48,further comprising: a fifth code segment including informationindicating a presence of said network control information.
 50. Thecomputer data signal according to claim 49, further comprising: a sixthcode segment for including information indicating a presence of saidoptics control information.
 51. The computer data signal according toclaim 48, further comprising: a fifth code segment including informationindicating a presence of said optics control information and/or saidnetwork control information.
 52. The computer data signal according toclaim 46, wherein said client information includes a control message.53. The computer data signal according to claim 46, wherein said clientinformation includes voice, data, and/or video from an end user.